SatisMeter's surveys for Shopify are meant to measure your customer's satisfaction with a completed order. By this we mean an order whose line items all have been shipped (marked as fulfilled) and received by the customer.
However, an order is marked as fulfilled when it gets shipped, which means that in most cases the customer hasn't received the order's contents yet. That's why SatisMeter waits a certain amount of days after the fulfilment date before actually sending the survey.
It is set to 7 days by default but it can be changed before launch or at any time in Settings page. You should set it to the amount that best suits your delivery times.
After waiting for the appropiate delay, SatisMeter will send a survey to your customer, using the email address contained in the customer's information. If the order doesn't have a specified customer, it will use the email address in the order's Contact Information.
And that's it! Remember that the whole process is automatic. There's no need to track when orders were fulfilled, or tell SatisMeter to send the survey.